The long term goal of the proposed research is to understand the control of eukaryotic cell proliferation by studying themolecular mechanisms involved in the replication of the human adenoviruses. The mechanism of initiation of adenovirus DNA replication will be investigated by 1) constructing and characterizing plasmids with mutations in the viral origin sequence. These plasmids will be tested for their ability to support different aspects of the initiation process in vitro, and for their ability to be replicated in vivo 2) constructing mutant adenovirus genomes with cis-acting defects in the origin of DNA replication. The mutant genomes will be used as the starting point for a genetic analysis of initiation. 3) further characterization of the activities of purified initiation proteins. The mechanism of chain elongation will be investigated by characterization of purified elongation factors using defined primer templates. Finally, the region of the viral origin sequence known to bind to a cell-encoded initiation factor will be assayed for possible function as a transcriptional regulatory element in uninfected cells.